I was having some trouble with that too on the original GMTK page (part of why I was late, but I got submitted after). What happens is you create a page for your game, and you can upload multiple times throughout the page for the game. You don't submit a file as much as you submit a page with a file on it. What the upload button does is say "hey you can press this button and create a page." You can also just submit a page you already have (you probably want to create it during the jam). Hope this helps!
Oh my goodness. The whole time we thought that the upload link on the jam page (would naturally) mean upload and publish for the jam. This is sort of exactly what happened to us, which is why our upload on the actual day never got the GMTK game jam title.... Is there still anyway we can share our game?
Thank you! I guess we really didnt learn our lesson and played with the deadline yet too closely again! :( I know we wont be able to get ratings but if anyone is interested in trying our game its https://monetheist.itch.io/monetheist
Click this link to join the jam :)
https://itch.io/jam/16507/add-game/701934?token=4SB3q0XIA1mrusmhCgVvgIOj7JI